<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <div id="a" style="color: red;">我是一个div</div>
    <script src="https://cdn.bootcdn.net/ajax/libs/jquery/3.7.1/jquery.js"></script>
    <script>
        let a = $("#a").css("color");
        console.log(a);
        $("#a").css("color", "blue");
    </script>

</body>
</html>